A major challenge in development of therapies for neurodegenerative diseases, including botulism, is the low efficiency and low specificity of existing treatments for targeting the therapeutic agents selectively to nerve cells without involvement of secondary sites of action. We have already demonstrated that we can specifically deliver a prototype cargo GFP into neuronal cells in vitro, ex vivo and in vivo, and w are now poised to translate this prototype cargo-delivery vehicle into a medically relevant inhibitory cargo-delivery vehicle(s) against botulism. We propose herein two antitoxin approaches toward combating paralysis from botulism, both based on our BoNT/A-HC platform. To demonstrate feasibility and versatility of our BoNT/A-HC-based platform for therapeutic biomolecule cargos targeted for neuronal-specific delivery, we propose to exchange the GFP cargo in our prototype GFP-BoNT/A-HC construct with two different types of cargo moieties, which will comprise the two aims of this proposal: Aim 1. Peptide/protein-based inhibitory cargo-delivery vehicles, and Aim 2. Biotin-streptavidin-linked inhibitory cargos-delivery vehicles. The proposed studies will be conducted in 3 phases for each construct of each aim: Phase I (R21 component, years 1-2) - Construction, purification, characterization and optimization of the BoNT/A-HC-based cargo-delivery vehicles and preliminary testing of the cargo-delivery vehicles for functionality in neuronal-specific cellular uptake in cultured neuronal cells. Phase II (R33 component, years 3-4) - Further optimization of cargo-delivery vehicle for stability, expression yield and intracellular cargo release. Testing the cargo-BoNT/A-HC delivery vehicle for functionality (delivery of cargo, inhibition of BoNT/A-mediated SNAP25 cleavage) in neuronal-specific cellular uptake in cultured neuronal cells; ex vivo in peroneal nerve-EDL muscle preparations; and in vivo after injection in mice. Phase III (R33 component, years 4-5) - Testing the cargo-BoNT/A-HC delivery vehicle for functionality and effectiveness in neuroprotective activity, such as protection from or recovery of neurotransmitter release after BoNT/A challenge, detection of increased expression of toxin-neutralizing scFv or camelid antibodies or SNAPI proteins encoded by DNA vectors.